1. Field of the Invention
The present invention relates generally to seats for motor vehicles and, more specifically, to a programmable seat belt damper assembly for a motor vehicle.
2. Description of the Related Art
It is known to provide seats for a motor vehicle. It is also known to provide a restraint system such as a seat belt to restrain an occupant in a seat of the motor vehicle. Typically, the restraint system includes a retractor attached to the seat or vehicle structure and having a spool attached to the seat belt. The spool is rotatably mounted to the retractor by a shaft. The retractor has a spiral spring on one end of the shaft to urge the spool in a direction for retracting the seat belt when not in use. Also, the retractor has a toothed sprocket on the other end of the shaft and a locking pawl to engage the sprocket to lock the shaft against rotation in the other direction to prevent belt unwinding. The locking pawl is typically operated by an inertia sensing mechanism coupled to an electrical actuator.
Although the above seat belt retractors have worked well, it is desirable to reduce occupant kinetic energy during a vehicle impact through programmed and limited seat belt pay out. It is also desirable to reduce seat back stiffness requirements of an integrated seat. Therefore, there is a need in the art to provide a programmable seat belt damper assembly for a motor vehicle.
Accordingly, the present invention is a programmable seat belt damper assembly for a seat belt in a motor vehicle. The programmable seat belt damper assembly includes a retractor operatively connected to the seat belt for winding and unwinding the seat belt. The programmable seat belt damper assembly also includes a rotary damper operatively connected to the retractor and having a magneto-rheological (MR) fluid therein. The programmable seat belt damper assembly further includes a controller electrically connected to the rotary damper to control an apparent viscosity of the MR fluid to increase and decrease a damping torque of the rotary damper for the unwinding of the seat belt.
One advantage of the present invention is that a programmable seat belt damper assembly is provided for a motor vehicle. Another advantage of the present invention is that the programmable seat belt damper assembly has a magneto-rheological damper for a seat belt. Yet another advantage of the present invention is that the programmable seat belt damper assembly permits limited highly damped torso travel to reduce occupant kinetic energy. Still another advantage of the present invention is that the programmable seat belt damper assembly reduces the seat back stiffness requirements of an integrated seat.